The present invention disclosed herein relates to an absorption modulator and a manufacturing method thereof.
Optical modulators are devices which change (modulate) the intensity, phase, polarization state, wavelength/frequency, or traveling direction of optical signals, which transmit information, by using external electrical, magnetic, mechanical, acoustic and optical units. Of those devices, a device which modulates the intensity or phase of an optical signal by using an electrical unit has been widely used because of its high operating speed (operating bandwidth) and controllability.
Representative examples of devices which modulate the intensity of light include a Mach-Zehnder modulator and an absorption modulator. The Mach-Zehnder modulator modulates a refractive index of a device material, caused by application of an electric field or current, and a phase shift of an optical signal into an intensity variation by using the interference effect of Mach-Zehnder interferometer. The absorption modulator controls (transmits or absorbs light) an optical absorption coefficient of a device material by applying an electric field or current to a device, and thus modulates the intensity of light propagated to the device material.
The Mach-Zehnder modulator has low temperature dependence and low wavelength dependence, but has relatively high optical loss and low yield. Meanwhile, the absorption modulator has low optical loss, but has high current consumption and low speed.